/**
* This file is part of ORB-SLAM2.
*
* Copyright (C) 2014-2016 Raúl Mur-Artal <raulmur at unizar dot es> (University of Zaragoza)
* For more information see <https://github.com/raulmur/ORB_SLAM2>
*
* ORB-SLAM2 is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* ORB-SLAM2 is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with ORB-SLAM2. If not, see <http://www.gnu.org/licenses/>.
*/


#include<iostream>
#include<algorithm>
#include<fstream>
#include<chrono>

#include<opencv2/core/core.hpp>

#include<System.h>

#include <unistd.h>

INITIALIZE_EASYLOGGINGPP

using namespace std;

void LoadImages(const string& strRoot,
                const string& strFile,
                vector<string>& vstrImageFilenames,
                vector<double>& vTimestamps);

int main(int argc, char **argv)
{
  if(argc != 5)
  {
    cerr << endl << "Usage: ./mono_tum path_to_vocabulary path_to_settings path_to_sequence frames.txt" << endl;
    return 1;
  }

  // Retrieve paths to images
  vector<string> vstrImageFilenames;
  vector<double> vTimestamps;
  string         strFile = string(argv[4]);

  LoadImages(string(argv[3]), strFile, vstrImageFilenames, vTimestamps);

  int nImages = vstrImageFilenames.size();

  // Create SLAM system. It initializes all system threads and gets ready to process frames.
  ORB_SLAM2::System SLAM(argv[1], argv[2], ORB_SLAM2::System::MONOCULAR, true);

  // Vector for tracking time statistics
  vector<float> vTimesTrack;
  vTimesTrack.resize(nImages);

  cout << endl << "-------" << endl;
  cout << "Start processing sequence ..." << endl;
  cout << "Images in the sequence: " << nImages << endl << endl;

  char    key;
  int     tk  = 2;
  // Main loop
  cv::Mat im;
  for(int ni  = 0; ni < nImages; ni++)
  {
    // Read image from file
    std::string filename = string(argv[3]) + "/" + vstrImageFilenames[ni] + ".jpg";
    cv::Mat im = cv::imread(filename, CV_LOAD_IMAGE_UNCHANGED);

    double tframe = vTimestamps[ni];

    if(im.empty())
    {
      cerr << endl << "Failed to load image at: " << filename << endl;
      return 1;
    }

    std::chrono::steady_clock::time_point t1 = std::chrono::steady_clock::now();

    // Pass the image to the SLAM system
    SLAM.TrackMonocular(im, tframe);


    std::chrono::steady_clock::time_point t2 = std::chrono::steady_clock::now();

    double ttrack = std::chrono::duration_cast<std::chrono::duration<double> >(t2 - t1).count();

    vTimesTrack[ni] = ttrack;

    key = cv::waitKey(tk);
    if(key == 's')
    {
      tk = tk > 0 ? 0 : 2;
    }
    else if(key == 'q')
    {
      return 0;
    }

    // Wait to load the next frame
    double T = 0;
    if(ni < nImages - 1)
      T = vTimestamps[ni + 1] - tframe;
    else if(ni > 0)
      T = tframe - vTimestamps[ni - 1];

    if(ttrack < T)
      usleep((T - ttrack) * 1e6);
  }

  // Stop all threads
  SLAM.Shutdown();

  // Tracking time statistics
  sort(vTimesTrack.begin(), vTimesTrack.end());
  float   totaltime = 0;
  for(int ni        = 0; ni < nImages; ni++)
  {
    totaltime += vTimesTrack[ni];
  }
  cout << "-------" << endl << endl;
  cout << "median tracking time: " << vTimesTrack[nImages / 2] << endl;
  cout << "mean tracking time: " << totaltime / nImages << endl;

  // Save camera trajectory
  SLAM.SaveKeyFrameTrajectoryTUM("KeyFrameTrajectory.txt");

  return 0;
}

void LoadImages(const string& strRoot,
                const string& strFile,
                vector<string>& vstrImageFilenames,
                vector<double>& vTimestamps)
{
  ifstream f;
  f.open(strFile.c_str());

  // skip first three lines
  string s0;
  double t = 0;

  while(!f.eof())
  {
    string s;
    getline(f, s);
    if(!s.empty())
    {
      stringstream ss;
      ss << s;
      string frame;
      vTimestamps.push_back(t);
      ss >> frame;
      vstrImageFilenames.push_back(frame);
      t += 0.02;
    }
  }
}
